The present invention relates to a sheath flow type photoanalysis apparatus in which fluid carrying particles such as cells flows in laminar conditions surrounded by sheath fluid through a capillary tube, a light beam having a constant wave length is applied on the flow of the fluid carrying particles, and properties of the particles such as kind, size, number and shape are measured from strength of light scattering and/or fluorescence caused by the particles and, more particularly, to a sheath flow type photoanalysis apparatus with means for correcting a position of the applied light beam for examination and the flow rate of the fluid carrying particles.
The present invention also relates to a method for correcting a position on which a light beam for examination is applied flow rate of fluid carrying particles in photoanalysis apparatus.
For example, U.S. Pat. No. 3,873,204, SCIENCE (Vol. 150, pp. 630-631, October, 1965), and Rev. Sci. Instrum. (Vol. 46, pp. 1021-1024, No. 8, August, 1975) have disclosed the photoanalysis apparatus in which fluid carrying particles such as cells flows through a capillary tube in laminar conditions surrounded by the sheath fluid, a light beam having a constant wave length is applied on the flow of the fluid carrying particles, and properties of the particles such as kind, size, number and shape are measured from strength of light scattering and/or fluorescence caused by the particles.
In the above-mentioned prior arts, flow of fluid carrying pilot particles such as control cells (for example, spherical cells such as blood of a chicken) or reference particles (spherical artificial particles) are subjected to optical measurement before the subject examination of particles starts and, from the result of the measurement an appropriate position on which the light beam for examination is applied is experientially determined. That is to say, since the flow rate of the fluid carrying particles to be examined is preset by utilizing the pilot particles which are different from the actual particles to be examined, the conventional method lacks reliability. Further, the operations for deciding the position on which the light beam is applied become thus tedious and complicated. When a difference in position occurs between the position on which the light beam for examination is applied and the flow of the fluid carrying particles by any disturbance during the actual examination of the particles, it is almost impossible to correct such a difference in position with the examination being continued.
In order to conduct the optimum optical measurement, it is necessary that the particles carried in the fluid flow through a spot of the light beam for examination. Thus, a width of the flow of the fluid carrying particles should appropriately be maintained constant. The width of the fluid carrying particles depends on its flow rate. Accordingly, there exists an optimum value to the flow rate of the fluid carrying particles in order to conduct an optimum optical measurement. Whereas, in the prior arts, the pilot particles are streamed prior to the examination of the particles to be examined and, the optimum value of the flow rate is supposed to be determined from the results of the optical measurement of the strength of light scattering and/or fluorescence caused by the pilot particles. Since the flow rate of the fluid carrying particles is determined by the pilot particles different from the actual particles to be examined, the prior art method has poor reliability. Further, the prior art method has a disadvantage that when a variation of the flow rate is occurred by any cause during the examination, it is not possible to correct the variation of the flow rate during the examination.